Relay connection unit mounted in vehicle

ABSTRACT

A Relay connection unit which is connected with a plurality of buses and relays a message to a different bus. The relay connection section comprises a data check section for detecting an error in a data section of a received message, a storage section for storing set data or/and the previously sent data for message rewriting use for each ID (identifier) attached to the message, and a data rewrite portion for rewriting the data section of the message in which the error is detected into the set data or the previously sent data stored in the storage section.

TECHNICAL FIELD

The present invention relates to a relay connection unit to be mountedon a car. More particularly the present invention relates to the relayconnection unit rewriting the data of a message in which an error hasbeen detected into a suitable data to relay the message as a completemessage.

BACKGROUND ART

A communication system to be mounted on a car is conventionally adoptedin which communication lines (hereinafter referred to as bus) connectedto electronic control units (ECU: Electronic Control Unit) controllingthe operation of appliances mounted on the car are connected with arelay connection unit such as a gateway to send and receive messagesamong the ECUs.

In recent years, with an increase in the function of the car, the numberof the ECUs has increased and the number of messages to be sent andreceived among the ECUs has rapidly increased. Therefore there is ademand that messages are efficiently sent and received among the ECUsand that a communication load factor of the bus is decreased.

To decrease the communication load, it is conceivable that stopping thetransmission of an incomplete message in which an error has occurred iseffective. In this case, an ECU to which the message is to be sent isincapable of periodically receiving the message.

The error message is generated in a case in which an improbable suddenchange has occurred in data relating to a car speed, temperature,illuminance, rainfall, and the like; a case in which data exceeds anordinary set range; and a case in which an improbable combination ismade among a plurality of data.

Thus in Japanese Patent Application Laid-Open No. 2002-16614 (patentdocument 1), there is proposed the gateway which does not transfer anincomplete message in which an error has occurred.

But in the gateway proposed in the patent document 1, whether themessage is to be transferred is determined after judging whether anerror has occurred by checking the content of the message. Thereforeunless the message is entirely received, it is impossible to determinewhether the message is to be transferred.

When it is determined that the message is not transferred, an ECU at areception side is incapable of periodically receiving the messageperiodically sent and received among the ECUs.

Further the gateway is capable of dealing with a store & forward methodof starting transmission after the message is entirely received, but isincapable of dealing with a cut-through method, having a favorabletransfer efficiency, of determining a destination to which the messageis transferred when the ID (identifier) is received before the messageis entirely received and starting transmission. Thus the gateway iscapable of decreasing the communication load factor of the bus, but hasroom for improvement in sending and receiving the message efficiently.

-   Patent document: Japanese Patent Application Laid-Open No.    2002-16614

DISCLOSURE OF THE INVENTION Problem to be Solved by the Invention

The present invention has been made in view of the above-describedproblems. It is an object of the present invention to provide a relayconnection unit capable of rewriting an incomplete message having anerror, sending the message as a complete message, and efficientlytransferring the complete message.

Means for Solving the Problem

To solve the above-described problem, the present invention provides arelay connection unit, to be mounted on a car, which is connected to aplurality of buses to which the relay connection unit relays a message.The relay connection unit has a data check section detecting an error ina data section of a received message; a storage section storing set dataor/and previously sent data for message-rewriting use for eachidentifier attached to the message; and a data rewrite portion rewritinga data section of the message in which the error has been detected bythe data check section into the set data or the previously sent datastored in the storage section.

The storage section storing the set data or/and the previously sent datafor message-rewriting use is a RAM; the storage section has a ROMstoring a routing table specifying a relay destination of the receivedmessage and break point discrimination data; and the RAM and the ROM areconnected to the data check section and the data rewrite portion.

When the power is turned on, the break point discrimination data of theROM is copied to the RAM from the ROM. Thereafter the break pointdiscrimination data is merely stored in the RAM and merely accessed tothe RAM.

In the relay connection unit having the above-described construction,the set data or/and the previously sent data for message-rewriting useare stored in the storage section (RAM) for each ID of the message.Therefore with reference to the set data or the previously sent datahaving an ID coincident with the ID of a message in which an error hasbeen detected, data can be rewritten.

When the data check section detects an error of the received message,the data rewrite portion rewrites the data section of an incompletemessage in which the error has been detected into the set data or thepreviously sent data stored in the RAM, so that the received message issent to the necessary bus as a complete message. Thereby it is possibleto prevent the transmission of an incomplete message including theerror. Further because the transfer of the message is not stopped, anECU which is to receive messages periodically is capable of periodicallyreceiving normal messages.

As the standard for detecting the error of the message, for example, thedata check section is provided with the following standards:

(1) In the case where the communication protocol of the communicationsystem is CAN and in the case where it is checked at a CRC that signalshaving the same level are successive in a message by 6 bits and that astaff error of not receiving the data of the message has occurred.

(2) A case in which data indicates an improbable sudden change. Forexample, a case in which an inside temperature and an outsidetemperature detected by a temperature sensor indicate an improbablesudden change, and a case in which a value detected by a car speedsensor changes more than a certain value with respect to a valuedetected thereby previously.

(3) A case in which a detected value is more than an upper limit valueor less than a lower limit value. For example, a case in which theoutside temperature detected by the temperature sensor exceeds 70° C. oris a default value.

(4) A case in which an improbable combination is made among a pluralityof data. For example, only one tire reversely rotates in the rotationalfrequency of rotations of four wheels.

The relay connection unit of the present invention has asending/receiving section relaying the message by using a cut-throughmethod of starting transmission at a time when the ID of the message isreceived, before the data check section checks the data section of thereceived message entirely.

That is, the store & forward method of determining whether it isnecessary to transfer the message after confirming whether the messagehas an error by checking the entire message data is not adopted in thepresent invention, but in the present invention, the cut-through methodof starting transmission with the data check section checking an errorof the message when the ID of the message is received is adopted. Inthis method, if an error is detected, the error is corrected and thecorrected message is sent. Therefore it is possible to relay the messageat a high speed.

As a method of transferring the message, it is possible to adopt thestore & forward method of starting transmission after receiving amessage entirely to send a message by correcting the data of the messagehaving an error. But the cut-through method is preferable to send themessage at a high speed.

The previously sent data stored in the RAM consists of a latestpreviously sent data stored by rewriting the previously sent data eachtime a message is sent.

By adopting the latest previously sent data to rewrite the error data,it is possible to minimize an error between correct sent data and thelatest previously sent data.

When the region of the RAM is large, entire sent data or data previouslysent several times may be stored to adopt the latest sent data.

It is preferable that the data section of the message to be checked bythe data check section consists of a plurality of sub-data; and breakpoint discrimination data indicating a break point of each sub-data isstored in the RAM; that the data check section detects a top bit ofsub-data in which an error has been detected by the error detectionportion thereof from the break point discrimination data stored in theRAM; that the data rewrite portion thereof rewrites the sub-data intothe set data or the previously sent data from the top bit of thesub-data; and that the rewritten data is stored in the RAM.

In the above-described construction, the entire data section of themessage in which the error has been detected is not rewritten, but onlythe sub-data subsequent to the sub-data in which the error has beendetected is rewritten into the set data or the previously sent data.Sub-data previous to the sub-data in which the error has been detectedis sent without rewriting it. Therefore the message can be efficientlysent.

When the data rewrite portion executes rewriting from the bit where theerror has occurred, data before rewriting and data after rewriting aremixedly present in one sub-data. Thus there is a possibility that aninappropriate data is generated. But in the present invention, thesub-data in which the error has occurred is entirely rewritten.Therefore it is possible to securely correct the sub-data in which theerror has occurred into the complete data.

In the break point discrimination data, the range of each sub-data isexpressed by making bits having an equal value successive. The value ofthe bit is changed at a break point position of the sub-data.

For example, when the break point discrimination data is expressed as“1110011110 . . . ”, it means that a range from a first bit to a thirdbit in which “1” is successive is a first sub-data, that a fourth bitand a fifth bit with “0” being successive are a second sub-data, andthat a range from a sixth bit to a ninth bit with “1” being successiveis a third sub-data. Therefore when an error is detected at an eighthbit, with reference to the break point discrimination data, it isdetected that a sub-data including the eighth bit starts from the sixthbit, and data subsequent to the sixth bit is rewritten into the set dataor the previously sent data.

The break point discrimination data may be provided for each sub-data toexpress a bit corresponding to the sub-data as “1” and a bituncorresponding to the sub-data as “0”. In this case, the break pointdiscrimination data is stored in the storage section by expressing thebreak point discrimination data for detecting the range of the firstsub-data as “1110000000 . . . ”, by expressing the break pointdiscrimination data for detecting the range of the second sub-data as“0001100000 . . . ”, and by expressing the break point discriminationdata for detecting the range of the third sub-data expressed as“0000011110 . . . ”.

It is preferable that the RAM stores both the set data and thepreviously sent data for message-rewriting use; and that for each ID ofthe message or/and each sub-data, the data rewrite portion selects theset data or the previously sent data as a value to be rewritten.

In the above-described construction, in dependence on the kind of data,the data rewrite portion is capable of selecting the set data or thepreviously sent data as the value to be rewritten. Thereby the datarewrite portion is capable of rewriting the data of the message in whichthe error has been detected into appropriate data.

For example, when the data of the message relates to door locking, a keyconfirmation result, a shift state, and the like, it is preferable torewrite the message in which the error has been detected into the dataset in advance. In the case of data relating to a car speed,temperature, an illuminance, a rainfall, and the like, it is preferableto rewrite the message in which the error has been detected into thepreviously sent data.

That is, a message relating to safety such as the door locking isrewritten into data in which importance is attached to safety, when themessage has an error. In the case of a message indicating a car speed,temperature, an illuminance, and the like whose content does notsuddenly change, the message in which an error has occurred is rewritteninto the previously sent data to maintain the content of the message byreflecting the content of the message sent latest.

Effect of the Invention

As described above, in the present invention, when the data checksection detects an error of the received message, the data rewriteportion rewrites the data section of the incomplete message in which theerror has been detected into the set data or the previously sent datastored in the RAM, so that the received message is sent to the necessarybus as the complete message. Thereby it is possible to prevent theincomplete message, namely, the useless message including the error frombeing sent.

The store & forward method of determining whether it is necessary totransfer the message after checking the entire data section of themessage is not adopted in the present invention, but in the presentinvention, the cut-through method of starting transmission when the IDof the message is received is adopted to relay the message with an errorin the data section of the message being corrected. Therefore it ispossible to relay the message at a high speed.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a communication system, to be mounted on a car, in which arelay connection unit of a first embodiment of the present invention isused.

FIG. 2 shows the format of a message.

FIG. 3(A) shows a routing table storage portion; and FIG. 3(B) shows abreak point discrimination data storage portion.

FIG. 4 shows data for rewriting use of a data storage portion.

FIG. 5 is a construction view showing a correlation in data processingto be executed inside the relay connection unit.

FIG. 6 is a flowchart of message transfer processing to be executed bythe relay connection unit.

FIG. 7 shows the flow of data when an error is not detected in amessage.

FIG. 8 shows the flow of data when an error is detected in a message.

FIG. 9 shows data for rewriting use in a second embodiment.

EXPLANATION OF REFERENCE NUMERALS AND SYMBOLS

-   10: communication system to be mounted on car-   11: bus-   20: relay connection unit-   23: CPU-   24-1, 24-2: ROM-   25: RAM-   26: comparison computation section-   27: data check section-   28: data rewrite portion-   29: error detection portion-   30: ECU (Electronic Control Unit)-   D: data for rewriting use-   D1: set data-   D2: previously sent data-   D3: break point discrimination data-   M: message-   MD: data section-   SD: sub-data-   T: routing table

BEST MODE FOR CARRYING OUT THE INVENTION

The embodiments of the present invention are described below withreference to the drawings.

FIGS. 1 through 7 show the first embodiment of the present invention.

In a communication system 10 of the first embodiment to be mounted on acar (hereinafter referred to as communication system 10), communicationlines (buses) CAN1, CAN2 using CAN as its communication protocol areconnected to each other via a relay connection unit (gateway) 20 toconstruct a communication network. A plurality of ECUs 30 (electroniccontrol units) is connected to each of the CAN 1, CAN 2. Appliances,switches, sensors, and the like to be controlled by the ECUs 30 areconnected thereto, but not shown in the drawings.

As shown in FIG. 1, the relay connection unit 20 is connected to the CAN1 and CAN 2 via a receiving section 21 and a sending section 22. Thereceiving section 21 and the sending section 22 are connected to a CPU23. The CPU 23 is connected to a storage section K shown in FIG. 3. Thestorage section K has a ROM 24-1 consisting of an identifier storageportion, a ROM 24-2 consisting of a break point discrimination datastorage portion, and a RAM 25 consisting of a data storage portion.

As shown in FIGS. 4 and 5, the CPU 23 has a comparison computationsection 26 determining whether it is necessary to relay a message anddetermining a bus through which the message is to be relayed withreference to a routing table T stored in the ROM 24-1 and a data checksection 27 composed of an error detection portion 29 detecting an errorof the message which is to be sent through the CAN determined by thecomparison computation section 26 and a data rewrite portion 28rewriting the message in which the error has been detected withreference to data D for rewriting use stored in the RAM 25.

As a transfer method, the comparison computation section 26 adopts acut-through method of starting to send a message before the comparisoncomputation section 26 receives the entire message, when it receives theID of the message and determines a destination to which the message isto be sent.

The error detection portion 29 checks whether the errors described aboveat (1) through (4) have occurred at a data section of the message whichis described later. For example, the error detection portion 29 checkswhether there is the staff error in the CRC as described in (1), whetherdata indicates the improbable sudden change as described in (2), whetherdata exceeds the set reference value as described in (3), and whetherthe improbable combination is made among a plurality of data asdescribed in (4). When an error is detected, the data rewrite portion 28rewrites the data section of the message.

As shown in FIG. 3(A), the ROM 24-1 of the storage section K stores therouting table indicating the correlation between the identifier (ID) andthe buses (CAN 1, CAN 2 . . . ) through which the message is sent. Asshown in FIG. 3(B), the ROM 24-2 stores the identifier, a DLC, and thebreak point discrimination data. As shown in FIG. 4, the RAM 25 storesthe data D for rewriting use. The data D for rewriting use includes aset data D1 for rewriting use, a previously sent data D2 for rewritinguse, and a break point discrimination data D3 provided for each ID ofthe message.

When a power is turned on, the break point discrimination data of theROM 24-2 is copied to the RAM 25. Thereafter the break pointdiscrimination data is stored in the RAM. Thereby it is possible toobtain the break point discrimination data by only an access to the RAM.

The set data D1 of the RAM 24 for rewriting use and the previously sentdata D2 thereof for rewriting use are the data for rewriting the messagein which an error has been detected. The set data D1 is set in advanceand has a constant value, whereas the previously sent data D2 is thedata previously sent and rewritten each time the message is sent. TheRAM 25 stores only the latest previously sent data for each ID.

Either the set data D1 or the previously sent data D2 is stored for eachID.

The set data D1 for rewriting use is stored for the data relating to adoor locking, a key confirmation result, a shift state, and the like.

The previously sent data D2 for rewriting use is stored for the datarelating to a car speed, parking brake information, temperature, anilluminance, a rainfall, and the like.

The break point discrimination data D3 is the data for discriminating abreak point of each sub-data described at the data section of themessage, as described later. The break point discrimination data D3makes it possible to recognize the range of the data section of themessage in which each sub-data is described. In rewriting the message inwhich the error has occurred, a data-rewriting range is determined withreference to the break point discrimination data D3.

In the break point discrimination data D3, the range of each sub-data isexpressed by making bits having an equal value successive. The value ofthe bit is changed at a break point position of the sub-data.

For example, as schematically shown in FIG. 2, when a data section MD ofa message M (ID100) is composed of a first sub-data SD1 (10 bits)relating to a car speed, a second sub-data SD2 (four bits) relating totemperature, and a third sub-data SD3 (two bits) relating to parkingbrake information . . . in the order of the first sub-data SD1, thesecond sub-data SD2, and the third sub-data SD3, the break pointdiscrimination data D3 is expressed as “11111111110000110 . . . ”, asshown in FIG. 4.

It can be recognized from the break point discrimination data D3 that inthe data section of a message having an ID of 100, the range from thefirst bit to the tenth bit in which “1” is successive is a firstsub-data SD1; that the range from the 11th bit to the 14th bit in which“1” is switched to “0” with “0” being successive is a second sub-dataSD2; and that the 15th bit and the 16th bit in which “0” is switched to“1” with “1” being successive is a third sub-data SD3.

The message M sent and received via the buses in the communicationsystem 10 of the first embodiment is composed of a format, asschematically shown in FIG. 2. The ID is described in an arbitrationfield. The data section MD is composed of a plurality of sub-data SDrelating to different information.

An SOF (start of frame) indicates the start of the message. A DLC (datalength code) indicates the length of the data section. A CRC indicates afield for checking an error in the transmission of the message.

The message transfer processing which is executed by the relayconnection unit 20 of the communication system 10 to be mounted on a caris described below with reference to FIGS. 5 and 6.

Initially when a power is turned on, the break point discrimination dataof the ROM 24-2 is copied to the RAM 25.

When the receiving section 21 of the relay connection unit 20 receives amessage (step S1 of FIG. 6), the comparison computation section 26 ofthe CPU 23 determines whether it is necessary to transfer the messageand the bus through which the message is to be sent with reference tothe routing table T, shown in FIG. 3(A), which is stored in the ROM 24-1(step S2 of FIG. 6).

Thereafter the error detection portion 29 of the data check section 27of the CPU 23 checks whether the message to be sent has an error (stepS3 of FIG. 6). A message not to be sent is discarded.

When the error detection portion 29 does not detect an error, themessage is sent to a necessary CAN via the sending section 22, as shownin FIG. 7 (steps S4, S5 of FIG. 6).

When the error detection portion 29 detects an error and when the datasection of the received message is to be rewritten into the previouslysent data D2, the message is sent to the necessary CAN via the sendingsection 22, as described above, and the message to be sent is written tothe RAM 25 as the previously sent data D2 to update the previously sentdata as the latest previously sent data (step S5 of FIG. 6).

On the other hand, when the error detection portion 29 detects that themessage has an error, as shown in FIG. 8, the data rewrite portion 28rewrites the data section of the message (step S6 of FIG. 6). At thistime, with reference to the break point discrimination data D3, sub-dataof the data section where the error has occurred is detected to rewritebits in the range from a top bit of the sub-data in which the error hasoccurred to a last bit of the data section as the set data D1 forrewriting use or the previously sent data D2 for rewriting use.

For example, when the data section of a message having an ID of 100 isexpressed as “10101010111111 . . . ” and when an error is detected atthe 14th bit to which the same bit is successive six times, withreference to the break point discrimination data D3 shown in FIG. 4, itis detected that the 14th bit is included in the second sub-datastarting from the 11th bit, and the bits subsequent to the 11th bitwhich is the top bit of the second sub-data are rewritten from “1111 . .. ” into the previously sent data D2, having the ID of 100, which isexpressed as “0011 . . . ”. The previously sent data D2 having the ID of100 shown in FIG. 4 is expressed as “aacc . . . ” by a hexadecimalnotation. The above-described message is rewritten by data in anecessary range of “1010101011001100 . . . ” which is expressed by abinary notation changed from “aacc . . . ”.

Thereby the message in which the error has occurred is rewritten into acomplete message which is sent to the necessary bus via the sendingsection 22 (step S7 of FIG. 6), as shown in FIG. 8.

In the above-described construction, when the error detection portion 29detects the error of the message received by the data check section 27,the data section of the message in which the error has been detected isrewritten into the set data D1 or the previously sent data D2 stored inthe RAM 25, so that the received message is sent to the necessary bus asthe complete message. Thereby it is possible to prevent the transmissionof an incomplete message including the error, namely, a useless message.

Whether transfer is necessary or not is not determined after checkingwhether the message has an error, but the error of the message iscorrected on the assumption that the message is transferred. Thereforeit is possible to start to send the message before the message isentirely received and efficiently send the message by using thecut-through method.

Further the data section of the message in which an error has beendetected is not entirely rewritten, but only the sub-data subsequent tothe sub-data in which the error has been detected is rewritten into theset data D1 or the previously sent data D2. The sub-data previous to thesub-data in which the error has been detected is sent without rewritingit. Therefore the message can be efficiently sent.

When the data rewrite portion executes rewriting from the bit where theerror has occurred, data before rewriting and data after rewriting aremixedly present in one sub-data. Thus there is a possibility that aninappropriate data is generated. But in the present invention, thesub-data in which the error has occurred is entirely rewritten.Therefore it is possible to securely correct the sub-data in which theerror has occurred into the complete data.

FIG. 9 shows the second embodiment.

The data of the second embodiment for rewriting use stored in the RAM 25is different from that of the first embodiment. The set data D1, thepreviously sent data D2, and the break point discrimination data D3 areprovided for each sub-data.

In detail, in the break point discrimination data D3, the bitcorresponding to given sub-data is “1”, whereas the bit uncorrespondingto the given sub-data is “0”. The break point discrimination data fordiscriminating the first sub-data SD1 of the first embodiment isexpressed as “11111111110000000 . . . ”. The break point discriminationdata for discriminating the second sub-data SD2 is expressed as“00000000001111000 . . . ”. The break point discrimination data fordetecting the range of the third sub-data SD3 is expressed as“00000000000000110 . . . ”.

Therefore in the message having the ID of 100, when an error is detectedat the 14th bit of the data section, the break point discrimination datahaving “1” at the 14th bit is searched. Because the 14th bit of thebreak point discrimination data of the second sub-data is “1”, it ispossible to detect that the error has occurred at the second sub-data.The data section of the message is rewritten from the 11th bit which isthe top bit of the second sub-data.

In the above-described construction, with reference to the break pointdiscrimination data, it is possible to efficiently execute the sub-datadiscrimination processing and the rewriting processing. In addition, itis possible to rewrite the sub-data into a value selected from the setdata D1 and the previously sent data D2 for each sub-data. That is, evenin the same message, it is possible to rewrite the first sub-data intothe previously sent data and the second sub-data into the set data.

Because other constructions of the second embodiment and the operationand effect thereof are similar to those of the first embodiment, thesame parts of the second embodiment as those of the first embodiment aredenoted by the same reference numerals and symbols as those of the firstembodiment.

1. A relay connection unit, to be mounted on a car, which is connectedto a plurality of buses to which said relay connection unit relays amessage, comprising: a data check section detecting an error in a datasection of a received message; a storage section storing set data or/andpreviously sent data for message-rewriting use for each identifierattached to said message; and a data rewrite portion rewriting said datasection of said message in which said error has been detected by saiddata check section into said set data or said previously sent datastored in said storage section.
 2. The relay connection unit to bemounted on a car according to claim 1, further comprising asending/receiving section relaying said message by using a cut-throughmethod of starting transmission at a time when said identifier of saidmessage is received, before said data check section checks said datasection of said received message entirely.
 3. The relay connection unitto be mounted on a car according to claim 1, wherein said storagesection storing said set data or/and said previously sent data formessage-rewriting use is a RAM; said storage section has a ROM storing arouting table specifying a relay destination of said received messageand break point discrimination data; and said data check section has anerror detection portion and a data rewrite portion and is connected tosaid RAM and said ROM; said error detection portion of said data checksection checks an error in said data section of said message; and saiddata rewrite portion rewrites said data section of said message in whichsaid error has been detected.
 4. The relay connection unit to be mountedon a car according to claim 3, wherein said RAM stores both said setdata and said previously sent data for message-rewriting use; and foreach identifier of said message or/and each sub-data, said data rewriteportion selects said set data or said previously sent data as a value tobe rewritten.
 5. The relay connection unit to be mounted on a caraccording to claim 3, wherein said previously sent data stored in saidRAM consists of a latest previously sent data stored by rewriting saidpreviously sent data each time said message is sent.
 6. The relayconnection unit to be mounted on a car according to claim 5, whereinsaid RAM stores both said set data and said previously sent data formessage-rewriting use; and for each identifier of said message or/andeach sub-data, said data rewrite portion selects said set data or saidpreviously sent data as a value to be rewritten.
 7. The relay connectionunit to be mounted on a car according to claim 5, wherein said datasection of said message to be checked by said data check sectionconsists of a plurality of sub-data; and break point discrimination dataindicating a break point of each sub-data is stored in said RAM; saiddata check section detects a top bit of sub-data in which an error hasbeen detected by said error detection portion thereof from said breakpoint discrimination data stored in said RAM; and said data rewriteportion thereof rewrites said sub-data into said set data or saidpreviously sent data from said top bit of said sub-data; and saidrewritten data is stored in said RAM.
 8. The relay connection unit to bemounted on a car according to claim 7, wherein said RAM stores both saidset data and said previously sent data for message-rewriting use; andfor each identifier of said message or/and each sub-data, said datarewrite portion selects said set data or said previously sent data as avalue to be rewritten.